The invention relates to the general field of distributing fluids, and it relates most particularly to installing electronic devices in pipes that convey a flow of natural gas.
A particular application of the invention lies in installing electronic devices in pipes made of polyethylene or of polyvinyl chloride (PVC), or of any other plastics material adapted to conveying fluids.
New energy sources are now available that are cleaner and renewable. Biomethane is one of these energy sources. Biomethane is obtained by fermenting agricultural, household, or industrial waste, or indeed fermenting sludge from sewage plants. Biomethane can be purified specifically to obtain quality that matches the properties required for being injected into a natural gas network. More precisely, the gas is odorized, monitored, and its pressure is regulated so that it can then be injected into a natural gas distribution network in order to be taken to consumers. Whereas natural gas has traditionally been distributed via a descending tree structure, natural gas must nowadays be distributed using a mesh structure as a result of the increasing number of biomethane distribution points.
In such a mesh structure, it is particularly important to know how gas is flowing, in particular in order to adapt production needs as a function of consumption. This knowledge about flows can be obtained by measuring the pressure, the flow rate, and physico-chemical parameters of the natural gas at numerous measurement points. In order to obtain accurate knowledge about flows, it is necessary to use a large number of measurement points. That leads to good knowledge about the quality of the gas, about its pressure, and about the integrity of the structure. That also makes it possible to control members of the structure well and thereby optimize billing of clients who receive the gas.
Sensors (e.g. pressure or flow rate sensors) are traditionally installed in pipes or in stations known as “pressure regulator stations”. That said, the locations where it is desired to take measurements are not always accessible for undertaking work in order to install sensors.
Those technical drawbacks have an impact on the cost and on the duration of work when installing sensors.
Another drawback of known techniques lies in the need to interrupt the flow of gas in the pipes while working on them.
In a first known technique, a pipe having gas flowing therein is pierced while using an isolation airlock or an apparatus for piercing a pipe conveying a flow of gas, and then an electronic system such as a sensor is inserted into the pipe.
In a second known technique, the electronic system is inserted by means of a probe.
Those known techniques present the following drawbacks:                installation work may require the flow of gas to be interrupted or at least the pressure of gas in the pipe to be reduced;        traditional electronic systems are very bulky (e.g. having a height of 1 meter (m) to 1.5 m), thereby making them installable only in locations that are sufficiently accessible;        traditional electronic systems require an external electrical power supply: that means that measurements can be taken only in the proximity of a power supply that is compatible with the European “ATEX” directive, well known to the person skilled in the art;        traditional electronic systems communicate the information they have recovered (if they are sensors) by means of wired networks; and        the cost of traditional electronic systems is too high, as indeed are the costs associated with installing such systems: that prevents a large number of sensors being installed.        
It may be observed that in order to enable an electronic system to be installed in a pipe without disturbing the flow of the fluid, installation work needs to take place in a pipe that, at some specific point, is straight between two ends. The point is selected so that the ratio of the distances between the two ends and that point is controlled (this ratio depends on the diameter of the pipe). This constraint further limits possibilities for installing a system using the prior technique.
The invention seeks specifically to mitigate some of those drawbacks, and it seeks in particular to obtain a device that is compact, easy to install, and capable of being inserted in a pipe while the pipe is conveying a flow of fluid.